Field of the Invention
The present invention generally relates to a satellite communication system. More specifically, the present invention relates to a satellite communication system in which a ground station is configured to communicate with a communication terminal through a satellite communication path. Also, the present invention generally relates to a satellite communication method.
Background Information
Satellite communication systems have emerged as an option for users to establish communication to terrestrial data networks, such as the Internet. Satellite communication systems typically utilize a very small aperture terminal (VSAT) at the user location. The VSAT allows users to access the terrestrial data networks. The VSAT is associated with a gateway or ground station which provides a point of connection to the terrestrial data networks for the satellite communication system.
Satellite communication systems are susceptible to the effects environmental conditions such as rain, snow, etc., (“rain fade”) which can result in service disruptions. With satellite communication systems, a radio frequency (RF) site diversity is utilized to remedy the service disruptions caused by localized rain fade.
Typically, two RF sites that are deployed 50-100 kilometers apart from each other are selectively utilized to avoid the service disruptions. In particular, in such satellite communication systems, two radio frequency transmitter/receivers (RFTs) at the RF sites are connected to the same gateway, respectively. Using two RF sites increases the availability of the satellite communication system since the joint probability of simultaneous rain fade on two distant locations is lower than the probability of rain fade on each individual site. The satellite communication systems take advantage of this fact by enabling switching between the RF sites when the signal is attenuated due to rain at one RF site and not on the other RF site.
In particular, with such satellite communication systems, an RF site where the rain fade is not severely attenuating the signal can be utilized. More specifically, when there are two different RF sites connected to the same gateway, one acts as the primary and the other acts as the backup. When the rain fade becomes severe enough at the primary RF site, then the signal from the gateway is routed to the backup RF site. This allows the satellite communication system to be available more often than if only one RF site is being used.